This invention relates generally to air intakes for aircraft engines, and, more specifically, to an air intake having a foreign object separator for a turboprop engine.
Aircraft gas turbine engines are particularly susceptible to damage from foreign objects introduced into the air inlets of the engines. This problem is significant with respect to relatively large foreign objects such as stones, gravel, birds, hail, ice, and the like, which, when introduced into the engine, can cause instant and substantial damage.
Apparatus are known in the prior art which are effective for removing foreign matter from engine inlet air. These apparatus fall into generally two categories: inlet particle separators effective for removing relatively small particles such as sand, dust and water from the airflow; and those defined herein as foreign object separators which are effective for removing relatively large foreign matter such as those as above described.
Ordinarily, foreign object separators are not effective for providing the protection offered by an inlet particle separator, and vice versa. More specifically, inlet particle separators, on the one hand, are designed for removing relatively small particles for increasing the effective life of the aircraft engine. Foreign object separators, on the other hand, are effective for removing relatively large objects which may be ingested during aircraft takeoff and the first segment of climb wherein substantial damage to the aircraft engine could result in a complete loss of power.
Furthermore, the Federal Aviation Adminstration (FAA) has specified ingestion requirements for turboprop aircraft engines in particular. These requirements include, for example, the ability of an aircraft engine to ingest without substantial loss of engine power, birds defined as being either small, medium, or large and having weights of three ounces, one and one half pounds, and four pounds, respectively. Relatively large foreign objects, for example, medium and large birds will have relatively large inertia when ingested into an aircraft engine upon takeoff or climb and, therefore, require an appropriate foreign object separator to prevent their ingestion into the engine.
Foreign object separators known in the prior art include, for example, sharp bends, screens, and valve structures, all of which result in undesirable pressure losses and increased complexity. Scavenge separators are known which require a portion of freestream inlet air to be channeled or bypassed away from the engine inlet and through the separator for carrying foreign objects overboard. These bypass air separators, therefore, require additional airflow which must be provided by increasing the effective area of the air inlet which results in a reduction of overall operating efficiency. Some of these prior art separators require swirl vanes or valve structures which in of themselves provide obstructions to airflow and which may be damaged by the impact of the these relatively large foreign objects.